The present invention relates generally to the preparation of aldehydes and more particularly to a method and apparatus for preparing aromatic aldehydes from aromatic compounds.
In general, aromatic aldehydes are useful as organic and chemical intermediates, as gas and oil additives, and as flavoring and fragrance agents, among others. More specifically, benzaldehyde has been used in the production of maraschino cherries and artificial jasmine odor, among others.
A variety of processes exist in the prior art for producing aromatic aldehydes from a corresponding aromatic compound. Many involve reacting the aromatic compound with carbon monoxide in the presence of various catalysts. For example, U.S. Pat. No. 3,948,998 (Fujiyama et al.) discloses a process for producing p-tolualdehyde by reacting toluene with carbon monoxide in the presence of a hydrogen fluoride-boron trifluororide catalyst. In U.S. Pat. No. 4,218,403 (Vanderpool), an alkyl-substituted phenyl aldehyde is prepared by reacting an alkyl-substituted benzene with carbon monoxide under super atmospheric pressure in the presence of a catalyst. U.S. Pat. No. 5,679,867 (Bruce et al.) discloses a process for making tolualdehyde by carbonylating toluene with either carbon monoxide or a source of carbon monoxide in a system free of hydrogen chloride and with a special catalyst. U.S. Pat. No. 5,910,613 (Schiraldi et al.) also discloses a process for producing aromatic aldehydes via carbonylation using triflic acid as a catalyst.
U.S. Pat. No. 4,554,383 (Knifton) discloses a method for preparing an aromatic aldehyde utilizing a xe2x80x9cmeltxe2x80x9d catalyst system comprising aluminum halide-alkyl pyridinium as well as various other prior art processes for producing aromatic aldehydes.
U.S. Pat. No. 5,877,330 (Kishimoto et al.) discloses the use of vanadium-containing catalysts for use in various types of oxidation reactions including oxidation reactions of aromatic hydrocarbons and various other compounds.
Despite the existence of a variety of methods for producing aromatic aldehydes from their corresponding aromatic compounds, there is a continuing need in the art for cost effective methods of producing aromatic aldehydes.
The present invention relates to a method and an apparatus for producing aromatic aldehydes such as benzaldehyde and metatolualdehyde, among others. Specifically, the method and apparatus of the present invention utilizes readily available and inexpensive raw materials, results in high conversion and selectivity rates, and thus provides increased production of the desired aldehyde. Generally, the raw materials used in the method and apparatus of the present invention include an aromatic compound and a source of oxygen, such as oxygen gas.
In one aspect, this invention is a process for the production of an aldehyde comprising providing a compound of formula R1xe2x80x94CX, wherein X is a group that leaves upon oxidation; reacting R1xe2x80x94CX and a source of oxygen to form R1xe2x80x94COH, wherein the reacting occurs in the liquid or vapor phase at a temperature of from 100xc2x0 C. to 200xc2x0 C. and in the presence of a catalyst consisting essentially of one or more of copper oxide and copper esters, wherein R1 is phenyl, which is unsubstituted or substituted by one or more identical or different radicals selected from (C1-C12)-alkyl, (C1-C12)-alkoxy, (C1-C12)-alkanoyloxy, (C1-C12)-alkanoyl, amino, hydroxyl, xe2x80x94CH2xe2x80x94Oxe2x80x94(C1-C12)-alkyl, xe2x80x94NHxe2x80x94(C1-C12)-alkyl, xe2x80x94NHxe2x80x94COxe2x80x94(C1-C12)-alkyl, or xe2x80x94Sxe2x80x94(C1-C12)alkyl; and separating the R1xe2x80x94COH.
Preferably, the source of oxygen is oxygen gas. The catalyst may be a liquid or a solid and is preferably cuprous oxide on a zirconia support. In a more preferred embodiment, the catalyst is a monolayer of cuprous oxide on a zirconia support. The cuprous oxide may be present at 2 to 20% by weight, or, more preferably, 2 to 10% by weight. The catalyst also may be selected from copper octoate and copper acetate. X may be xe2x80x94H3, and R1 may be meta-methylphenyl. The reacting may be in the vapor phase and may be in one tube reactor or two or more tube reactors connected in parallel. The process may also include stopping the reaction of R1xe2x80x94CX and the source of oxygen in a first of the two or more tube reactors while passing the R1xe2x80x94CX and the source of oxygen through a second of the two or more tube reactors and regenerating the catalyst in the first tube reactor. The process may be continuous.
In a second aspect, this invention is method of preparing metatolualdehyde that includes providing meta-xylene and a source of oxygen; providing a tube reactor loaded with a catalyst consisting essentially of one or more of copper oxide and copper esters; passing the meta-xylene and the source of oxygen through the tube reactor at a temperature of between about 100xc2x0 C. and 200xc2x0 C.; and recovering the metatolualdehyde.
In a third aspect, this invention is a method of preparing benzaldehyde that includes providing toluene and a source of oxygen; providing a tube reactor loaded with a catalyst consisting essentially of one or more of copper oxide and copper esters; passing the toluene and the source of oxygen through the tube reactor at a temperature of between about 100xc2x0 C. and 200xc2x0 C.; and recovering the benzaldehyde.
In a fourth aspect, this invention is a process for the production of an aldehyde comprising providing a compound of formula R1xe2x80x94CX, wherein X is a group that leaves upon oxidation; reacting R1xe2x80x94CX and a source of oxygen to form R1xe2x80x94COH, wherein the reacting occurs in the liquid or vapor phase at a temperature of from 100xc2x0 C. to 200xc2x0 C., at a weight hourly space velocity of greater than one, and in the presence of a catalyst, wherein R1 is phenyl, which is unsubstituted or substituted by one or more identical or different radicals selected from (C1-C12)-alkyl, (C1-C12)-alkoxy, (C1-C12)-alkanoyloxy, (C1-C12)-alkanoyl, amino, hydroxyl, xe2x80x94CH2xe2x80x94Oxe2x80x94(C1-C12)-alkyl, xe2x80x94NHxe2x80x94(C1-C12)-alkyl, xe2x80x94NHxe2x80x94COxe2x80x94(C1-C12)-alkyl, or xe2x80x94Sxe2x80x94(C1-C12)-alkyl; and separating the R1xe2x80x94COH.